回複：I-485 case is complicated situation, please give some idea.

1. Do I need to notify USCIS for 2nd FP? or just wait for notice?
-No, just wait for RFE if USCIS need you to do that.

2. Will my case be delayed again because I need to redo the FP again and then do the background check AGAIN?
-No, they have used your first FP to the background check.
3. Is that possible that my case will be approved in Oct without 2nd FP?
-Yes, they may approve your I-485, and then ask you to do FP before they issue the GC to you.